Intraocular lenses and process for the producing molded-in type intraocular lenses

ABSTRACT

A one-piece intraocular lens having an optic portion and a haptic portion, the optic portion being formed of a copolymer obtained by copolymerization of predetermined amounts of 2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate, 2-phenylethyl (meth)acrylate, alkyl (meth)acrylate and a crosslinking monomer, the haptic portion being formed of polymethyl methacrylate, a process for the production thereof, and a soft intraocular lens having an optic portion and a haptic portion formed of a soft material, the haptic portion having a bendable portion having specific functions, the one-piece intraocular lens being insertable into an eye through a small incision with the optic portion being bent, the soft intraocular lens permitting the prevention of the deformation of the soft optic portion caused by the shrink of a capsule when the soft intraocular lens is inserted into an eye.

This application is 35 U.S.C. § 371 of PCT/JP98/05370, filed Nov. 30,1998

FIELD OF THE INVENTION

The present invention relates to an intraocular lens and a process forthe production of a one-piece intraocular lens. More specifically, thepresent invention particularly relates to a one-piece intraocular lenswhich can be inserted through a small incision by bending its opticportion when it is inserted into an eye, a process for the efficientproduction of the same, and a soft intraocular lens which permits theprevention of deformation of a soft optic portion caused by the shrinkof a capsule after intraocularly inserted.

TECHNICAL BACKGROUND

In recent years, with an increase in the population of aged people,senile cataract patients are distinctively increasing. A treatmentagainst cataract is carried out by removing a clouded nucleus and cortexof a crystalline lens and either correcting a vision with an eyeglass ora contact lens or inserting an intraocular lens, while it is generalpractice to employ a method in which a crystalline lens as a whole isremoved and an intraocular lens is fixed.

The above intraocular lens comprises an optic portion which functions asa substitute lens for the crystalline lens removed due to cataract and anarrow and long filament-like haptic portion which is to fix and holdthe optic portion in the central position in a capsule. It is known thatthe above intraocular lens includes an intraocular lens of a type whichis formed by separately producing the haptic and optic portions andlater combining them (sometimes called two-piece or three-piece type),and a one-piece intraocular lens formed by integrally producing thehaptic and optic portions (sometimes called one-piece type). As amaterial for the optic portion, there has been mainly used polymethylmethacrylate (to be referred to as “PMMA” hereinafter) which is a hardmaterial. The reason for the use of PMMA as a material for the aboveplanting intraocular lens is that it is transparent and excellent instability in organisms (biocompatibility) and that it has adequatemachinability and can provide elaborate lenses stably. As a material forthe hepatic portion for holding the above optic portion formed of PMMA,for example, a mono-filament of PMMA, polypropylene or polyimide hasbeen used. Concerning the bonding of the above optical portion andhaptic portion, as one type, a small hole for attaching the hapticportion is made in the optic portion, the haptic portion is inserted inthe small hole after the optic portion is completed, then the hapticportion is fixed to the optic portion by staking or laser (two-piece orthree piece type), or there is a one-piece type integrally formed ofPMMA.

On the other hand, with a widened use of an ultrasonic emulsificationaspiration method in recent years, there has been developed anintraocular lens which can be inserted through a small incision, fordecreasing postoperative astigmatism and an operation stress. That is,the above intraocular lens is formed of a soft material as a materialfor the optic portion so that it can be bent so as to be insertedthrough a small incision.

Since, however, the soft material is difficult to machine, i.e., cut andpolish unlike a conventional PMMA, the production of the optic portiongenerally uses a cast-molding method in which a monomer, a prepolymer oran oligomer as a material for forming the optic portion is polymerizedin a mold. Further, since it is also difficult to mechanically make asmall hole in the method of attaching the haptic portion, it is requiredto employ a method different from the conventional method.

For producing the above soft intraocular lens, various method, forexample, shown below have been so far proposed.

(1) A method of producing an intraocular lens having aneasily-non-removable haptic portion, in which the end portion of afilament constituting the haptic portion is permanently deformed to forma mechanical engagement portion having the form of a bulb, etc., oranother filament having a mechanical engagement portion is bonded to theend of the former filament to form a terminal portion of the hapticportion and an optical member is mold-shaped with the terminal portioninserted (JP-A-62-142558, JP-A-62-152450).

(2) A method of producing an intraocular lens, in which a soft opticalmaterial is polymerized in a mold, then, a mold with a polymerized softoptical material in it is cooled to harden the soft material, a smallhole in which a haptic portion is to be inserted and a small hole inwhich an anchor filament is to be inserted are mechanically made in theoptic portion, then, the haptic portion is inserted in thehaptic-portion-inserting small hole, a filament formed of the samematerial as that of the haptic portion is inserted in theanchor-filament-inserting small hole, an intersection of the hapticportion and the anchor filament is irradiated with a laser beam to fusethe haptic portion to the hole, and further, irradiation with a laserbeam is effected along the inserting holes (JP-A-4-292609).

(3) A method of producing a foldable intraocular lens, in which a rod ofa homopolymer or a copolymer of 2-hydroxyethyl methacrylate (HEMA) wasprepared as a foldable optical member, the rod is placed in a tubularmold, a haptic portion is formed around the rod by polymerizing a hardmaterial such as PMMA, then, a disc is obtained by cutting the rod,ground and polished to produce an intraocular lens and the lens ishydrated (allowed to contain water) (JP-A-4-295353).

(4) A method in which a flat plate is prepared from a crosslinkedacrylic resin material, placed on a holder and cut into a disc with alathe at a low temperature, the disc is cut to form a soft optic portionand then the soft optic portion is provided with haptic portions toobtain a three-piece type intraocular lens, or the above flat plate iscut into a material in the form of a lens to obtain an intraocular lenshaving a foldable optic portion and a soft haptic portion formed of thesame soft material as the material of the optic portion (JP-A-1-158949).

(5) A method of producing an intraocular lens, in which an opticalmaterial having a diameter of 5 mm and a height of 20 mm was prepared bypolymerization and then placed in the center of a cylinder having aninner diameter of 15 mm and a height of 20 mm, a monomer for forming amaterial of a haptic portion is polymerized in a circumferential portionthereof, and then, a material in the form of an intraocular lens isprepared by cutting and immersed in an alcohol for about 48 hours tosoften the optic portion by esterification (JP-A-5-269191).

However, the above methods of producing intraocular lenses all havedefects that the procedures are complicated and that the productionefficiency is poor. That is, in the above method (1), it is required tomake a plastic filament which is to form the haptic portion into acomplicated form. The filament which is to form the haptic portion has adiameter of approximately 0.15 mm, and it is required to provide anextremely complicated and fine step for making the end portions of allthe filaments in one form by melting the under heat. The haptic portionis required to have a form suitable for holding and fixing in an eye,and the form thereof is elaborately made by thermoforming. That is, whena soft optical material is produced in a mold so as to surround theabove elaborately made haptic portion, the haptic portion is againexposed to heating and pressing steps, and the form and dimensionsthereof may be altered.

In the above method (2), it is required to cool the material and maketwo holes, the hole for inserting the haptic portion and theanchor-filament-inserting hole which intersects with the former hole,and it is also required to insert the haptic portion and the anchorfilament in the holes and attain the fusing of the haptic portion andthe filling the hole with filament by repeatedly irradiating them withlaser beam. Therefore, considerably complicated procedures are required.

In the above method (3), the optic portion is formed of a materialcomposed mainly of HEMA, and a lens at the time of cutting is hard, butit is made soft by hydration after the cutting. HEMA shows a differencein water absorptivity from one lot to another, and it is difficult tomaintain constant performances of intraocular lenss. Further, it takes atime during an operation to hydrate the intraocular lens, and further,when an intraocular lens is hydrated in advance, it is difficult to theintraocular lens in a sterile state.

Further, in the above method (4), the material of the haptic portion isthe same as the material of the optic portion, and the haptic portion istherefore soft. The haptic portion of a conventional intraocular lenshas a diameter of approximately 0.1 to 0.2 mm, and the haptic portion isconsiderably soft. It is therefore thought that maintaining an hapticportion angle is difficult and that the positional stability of theoptic portion in a capsule is difficult.

In the above method (5), no haptic portion material having reactivitywith an alcohol can be used. It is therefore not possible to use PMMAwhich is generally used at present.

Further, a chemical reaction is caused on the optic portion after theform of an intraocular lens is made by precision cutting and polishing,and the form of the optic portion (change in curvature, thickness,optical radius, etc.) may be changed, and it is difficult to maintainthe haptic portion angle during processing.

Meanwhile, when the optic portion and the haptic portion are bonded in atwo-piece or three-piece intraocular lens, an angle is provided in quitea few cases such that the haptic portion forms an angle of approximately5 to 10 degrees with a plane at right angles with the optical axis ofthe optic portion. The above is for stable registering after the lens isfitted in a capsule.

Further, in the above one-piece type intraocular lens, the optic portionand the haptic portion are integrally formed in many cases. FIG. 7 showsa plan view of a conventional one-piece intraocular lens. FIG. 8schematically shows a side view of the haptic portion of a conventionalone-piece intraocular lens. In these Figures, numeral 6 indicates theoptic portion, and numeral 7, 7′ is the haptic portion. In the form ofthe haptic portion of a one-piece type intraocular lens, an angle ofapproximately 5 to 10 degrees is provided in many cases as shown in FIG.8, like the above two-piece or three-piece type intraocular lens.

Further, as far as the form of the haptic portion is concerned, there isan intraocular lens called a wing type. FIG. 9 schematically shows aside view of an wing type intraocular lens. The haptic portion 7,7′rises at an angle of approximately 5 to 10 degrees and then comes to beparallel with a plane at right angles with the optical axis of the opticportion. Intraocular lenses of all the types are designed such that thelenses inserted in capsules can be stably fixed in the capsules.

Further, it is known that the haptic portion of the above softintraocular lens is also designed as a type provided with an angle ofapproximately 5 to 10 degrees or as a wing type.

Meanwhile, when an intraocular lens is inserted in a capsule, the innerdiameter of the capsule shrinks to approximately 10 mm, and the hapticportion is accordingly compressed. Generally, the optic portion issupported by the function of the elastic force generated by the abovecompression of the haptic portion. In this case, part of the elasticforce is transmitted to the optic portion. When the optic portion isformed of a hard material such as PMMA, almost no problem is caused bythe transmission of the above elastic force. However, when the opticportion is formed of a soft material, depending upon how an intraocularlens is inserted in a capsule, the optic portion may be deformed ordistorted, or the displacement of a lens may not be constant, due to theabove elastic force transmitted to the optic portion, so that theresolution and lens strength may not be attained as designed.

DISCLOSURE OF THE INVENTION

Under the circumstances, it is a first object of the present inventionto provide a one-piece type intraocular lens having an optic portionhaving an elasticity sufficient to be bent when the intraocular lens isinserted in an eye and a haptic portion which is like a haptic portionused in a conventional intraocular lens formed of PMMA and is forholding and fixing the optic portion in the eye and which is not easilyremovable.

Further, it is a second object of the present invention to provide aprocess for efficiently producing the above one-piece type intraocularlens free of a variability in product quality without requiring anycomplicated steps.

Further, it is a third object of the present invention to provide a softintraocular lens whose optic portion is deformed or distorted in almostno case when the haptic portion thereof is compressed due to the shrinkof a capsule after the soft intraocular lens is inserted in the capsule.

The term “haptic portion” in the present specification refers to aplurality of members extending from the optic portion as shown, e.g., inFIG. 4, and is used in this sense throughout the specification.

The present inventors have made diligent studies to achieve the aboveobjects, and have found that the above first object can be achieved by aone-piece type lens having an optic portion and a haptic portion, saidoptic portion being formed of a copolymer obtained by polymerization ofa monomer mixtures containing 2-[2-(perfluorooctyl)ethoxy]-1-methylethyl(meth)acrylate, 2-phenylethyl (meth)acrylate, alkyl (meth)acrylate ofwhich the alkyl group has a specific number of carbon atoms and acrosslinking monomer in a predetermined amount ratio and said hapticportion being formed of PMMA.

It has been also found that the above second object can be achieved asfollows.

The above one-piece type lens can be easily and efficiently producedwithout a variability in product quality by polymerizing the aboveoptic-portion-forming monomer mixture with keeping the monomer mixturein contact with a haptic-portion-forming material containing PMMA, orpolymerizing a haptic-portion-forming monomer containing methylmethacrylate with keeping the haptic-portion-forming monomer in contactwith an optic-portion-forming material formed of a copolymer obtained bypolymerization of the above monomer mixture, to integrate theoptic-portion-forming material and the haptic-portion-forming material,and cutting and polishing the integrated product.

Further, it has been found that the above third object can be achievedby a soft intraocular lens whose haptic portion is provided with abendable portion which can absorb at least part of an externalcompressive force exerted on the haptic portion by deformation so thatthe bendable portion can decrease the force to be transmitted to theoptic portion.

The present invention has been completed on the basis of the abovefindings.

That is, according to the present invention, there is provided aone-piece intraocular lens having an optic portion which functions as asubstitute lens for a crystalline lens and a haptic portion for fixingand holding the optic portion in a predetermined position in an eye, theoptic portion being formed of a copolymer obtained by polymerization ofa monomer mixture containing

(a) 5 to 20% by weight of 2-[2-(perfluorooctyl)ethoxy]-1-methylethyl(meth)acrylate of the formula (I),

wherein R¹ is hydrogen or methyl,

(b) 40 to 70% by weight of 2-phenylethyl (meth)acrylate of the formula(II),

wherein R² is hydrogen or methyl,

(c) 25 to 50% by weight of alkyl (meth)acrylate of the formula (III),

wherein R³ is hydrogen or methyl and R⁴ is a C₄-C₁₂ linear, branched orcyclic alkyl group, and

(d) 0.5 to 5% by weight, based on the total amount of the components (a)to (c), of a crosslinking monomer,

the haptic portion being formed of polymethyl methacrylate (the aboveintraocular lens will be sometime referred to as “intraocular lens 1”hereinafter).

According to the present invention, further, there is provided a processfor the production of a one-piece intraocular lens having an opticportion which functions as a substitute lens for a crystalline lens anda haptic portion for fixing and holding the optic portion in apredetermined position in an eye, the process comprising polymerizing anoptic-portion-forming monomer mixture containing 5 to 20% by weight of2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of the aboveformula (I), (b) 40 to 70% by weight of 2-phenylethyl (meth)acrylate ofthe above formula (II), (c) 25 to 50% by weight of alkyl (meth)acrylateof the above formula (III) and (d) 0.5 to 5% by weight, based on thetotal amount of the components (a) to (c), of a crosslinking monomer,with keeping the monomer mixture in contact with ahaptic-portion-forming material containing polymethyl methacrylate, orpolymerizing a haptic-portion-forming monomer containing methylmethacrylate with keeping the haptic-portion-forming monomer in contactwith an optic-portion-forming material formed of a copolymer obtained bypolymerization of the above monomer mixture, to integrate theoptic-portion-forming material and the haptic-portion-forming material,and cutting and polishing the integrated product.

Further, according to the present invention, there is provided a softintraocular lens having an optic portion formed of a deformable softmaterial which functions as a substitute lens for a crystalline lens anda haptic portion which is formed of arm-like two members extendingoutwardly from circumferential portions of the optic portion and is forfixing and holding the optic portion in a predetermined position in aneye, the haptic portion being provided with a bendable portion which,when a compressive force is externally exerted on the haptic portion soas to move at least any site of the haptic portion toward the opticportion, can absorb at least part of the external compressive force bydeformation and decreases the force to be transmitted to the opticportion (the above soft intraocular lens will be sometimes referred toas “intraocular lens 2” hereinafter).

In the present invention, the term “(meth)acrylate” includes acrylateand methacrylate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a perspective view of one example of a disc which is formedof PMMA and has a cylindrical concave portion.

FIG. 1(b) is a side view of the same.

FIG. 2(a) is a perspective view showing a state where a monomer mixturefor forming an optic portion is charged in the concave portion of thedisc shown in FIG. 1, and

FIG. 2(b) is a side view showing the same.

FIG. 3 is a perspective view for explaining the cutting of a materialwith a milling machine for a one-piece type intraocular lens.

FIG. 4(a) is a front view of one example of the intraocular lens(intraocular lens 1) of the present invention, and

FIG. 4(b) is a side view of the same.

FIG. 5(a) is a front view of one example of the soft intraocular lens(intraocular lens 2) of the present invention, and

FIG. 5(b) is a side view of the same.

FIG. 6 is an enlarged view of part shown in FIG. 5(b).

FIG. 7 is a plan view of one conventional intraocular lens.

FIG. 8 is a schematic side view of a conventional one-piece intraocularlens.

FIG. 9 is a schematic side view of a wing type intraocular lens.

FIG. 10 shows how a compression holding test is carried out.

FIG. 11 shows results of a compression holding test.

FIG. 12(a) shows the effect of compressive force exerted on the hapticportion of a conventional lens having an optic portion formed of a softmaterial.

FIG. 12(b) shows the effect in a conventional lens of compressive forceexerted on an optic portion of a soft material and partial dispersionfrom the optic portion.

FIG. 12(c) shows in lenses according to the present inventioncompressive force is dispersed at least twice before reaching the opticportion.

BEST MODES FOR PRACTICING THE INVENTION

The one-piece intraocular lens (intraocular lens 1) of the presentinvention has an optic portion which functions as a substitute lens fora crystalline lens and a haptic portion for fixing and holding the opticportion in a predetermined position in an eye.

The above optic portion is formed of a copolymer obtained bycopolymerization of a monomer mixture containing the followingcomponents (a) to (d). Component (a), i.e.,2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of the formula(I), is an essential component for decreasing the surface stickingnature of the optic portion of the intraocular lens and imparting theintraocular lens with the function that the intraocular lens can restoreits original shape in a proper time period of approximately 20 to 60seconds to stabilize itself.

In the formula (1), R¹ is hydrogen or methyl, while R¹ is preferablymethyl.

Component (b), i.e., of 2-phenylethyl (meth)acrylate of the formula(II), is a component for imparting the optic portion of the intraocularlens with a high refractive index.

In the formula (2), R² is hydrogen or methyl, while R² is preferablymethyl.

Component (c), i.e., alkyl (meth)acrylate of the formula (III), is acomponent for imparting the optic portion of the intraocular lens withhigh flexibility.

In the formula (III), R³ is hydrogen or methyl, while R³ is preferablyhydrogen. R⁴ is a C₄-C₁₂ linear, branched or cyclic alkyl group.Examples of the alkyl (meth)acrylate of the formula (III) preferablyinclude n-butyl acrylate, isobutyl acrylate, isoamyl acrylate, n-hexylacrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate,isooctyl acrylate and decyl acrylate, isodecyl acrylate. These acrylatesmay be used alone or in combination.

Component (d), i.e., a crosslinking monomer, is a component forpreventing the deformation of the optic-portion-forming material duringthe polymerization and improving the optic portion of the intraocularlens in mechanical strength.

Examples of the above crosslinking monomer include ethylene glycoldimethacrylate (to be referred to as “EDMA” hereinafter), diethyleneglycol dimethacrylate, triethylene glycol dimethacrylate, tetraethyleneglycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,4-butanedioldiacrylate and 1,6-hexanediol dimethacrylate. These monomers may be usedalone or in combination.

In the present invention, the content of each component in the monomermixture is as follows. On the basis of the total amount of components(a) to (c), the content of component (a) is 5 to 20% by weight, thecontent of component (b) is 40 to 70% by weight, and the content ofcomponent (c) is 25 to 50% by weight. When the content of component (a)is less than 5% by weight, there may be no sufficient effect ondecreasing the surface sticking nature of the optic portion of theintraocular lens and imparting the intraocular lens with the functionthat the intraocular lens can restore its original shape in a propertime period, e.g., of approximately 20 to 60 seconds to be stabilized.When it exceeds 20% by weight, the capability of restoring the shape ofthe optic portion tends to be decreased. In view of an effect ondecreasing the surface sticking nature and the shape restoringcapability, the content of component (a) is preferably 7 to 15% byweight.

When the content of component (b) is less than 40% by weight, it isdifficult to impart the optic portion of the intraocular lens with anadequate refractive index. When it exceeds 70% by weight, the opticportion comes to show decreased flexibility and is hard to be bent intoa small size. In view of the refractive index and flexibility of theoptic portion, the content of component (B) is preferably 42 to 63% byweight.

When the content of component (c) is less than 25% by weight, it isdifficult to impart the optic portion of the intraocular lens withsufficient flexibility. When it exceeds 50% by weight, the surfacesticking nature of the optic portion may increase. In view of theflexibility and the surface sticking nature of the optic portion, thecontent of the component (c) is preferably 30 to 46% by weight.

On the other hand, the content of the crosslinking monomer as component(d) is 0.5 to 5% by weight based on the total amount of the abovecomponents (a) to (c). When the content of component (d) is less than0.5% by weight, the effect of use of the crosslinking monomer is notsufficiently produced. When it exceeds 5% by weight, the number ofcrosslinkage points increases to excess so that the optic portion isfragile and that the mechanical strength of the optic portion maydecrease. In view of the effect and the mechanical strength, the contentof the crosslinking monomer is preferably 1 to 4% by weight.

In the present invention, the monomer mixture may contain a monomercapable of absorbing ultraviolet light as required.

The above monomer capable of absorbing ultraviolet light includes, forexample, a compound of the formula (IV),

wherein X is hydrogen or chlorine and R⁵ is hydrogen or methyl.

Specific example of the compound of the above formula (IV) include5-chloro-2-[2-hydroxy-5-(β-methacryloyloxyethylcarbamoyloxyethyl)]phenyl-2H-benzotriazole(to be referred to as “CHMP” hereinafter) and2-[2-hydroxy-5-(β-methacryloyloxyethylcarbamoyloxyethyl)]-phenyl-2-H-benzotriazole.

Further, as other ultraviolet absorbent monomer, there may be used2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-(2′-methacryloyloxyethyl)benzotriazoleof the following formula.

The content of the above monomer capable of absorbing ultraviolet light,based on the total amount of the components (a) to (c), is preferably0.05 to 3% by weight, particularly preferably 0.1 to 2% by weight. Whenthe above content is less than 0.05% by weight, no effect on theprevention of ultraviolet light can be expected. When it exceeds 3% byweight, the effect thereof is almost no further increased, or it isdisadvantageous in view of an economic performance.

In the present invention, further, the above monomer mixture may containa coloring monomer such as a polymerizable dyestuff as required forcoloring the optic portion of the intraocular lens.

In the intraocular lens of the present invention, the optic portionwhich functions as a substitute lens for a crystalline lens is formed ofa copolymer obtained by copolymerization of the above components (a) to(d) and optional components such as the above monomer capable ofabsorbing ultraviolet light and the above coloring monomer.

The above copolymer is produced by adding a polymerization initiator tothe above monomer mixture, fully stirring the resultant mixture toprepare a homogeneous monomer mixture, and polymerizing the homogeneousmixture according to a general method. The above general method refersto a method in which a radical polymerization initiator is added, andthen the mixture is temperature-increased stepwise or continuously from40 to 120° C. or the mixture is irradiated with ultraviolet light orvisible light.

Specifically, the above radical polymerization initiator can be selectedfrom generally known radical polymerization initiators includingazo-containing initiators such as azobisvaleronitrile andazobisisobutyronitrile (to be referred to as “AIBN” hereinafter) andorganic peroxides such as bis(4-t-butylcyclohexyl)peroxydicarbonate. Theamount of the above initiator based on the total monomer amount ispreferably 0.1 to 5% by weight.

In the one-piece intraocular lens of the present invention, the hapticportion for fixing and holding the above optic portion in apredetermined position in an eye is formed of polymethyl methacrylate,and the haptic portion and the optic portion are required to beintegrated.

Concerning the form of the above one-piece intraocular lens, there areknown a lens of which the haptic portion form has a angle ofapproximately 5 to 10 degrees and a sp-called wing type lens of whichthe haptic portion rises at an angle of approximately 5 to 10 degreesand comes to be horizontal in an end portion thereof.

When one-piece intraocular lens have the above forms, the optic portionundergoes no deformation even when the haptic portion is compressed(after the intraocular lens is inserted) so long as the optic portion isformed of a hard material such as PMMA. Further, the positionalstability of the optic portion in an eye is presumably excellent sincethe displacement of the optic portion is low when the haptic portion iscompressed.

However, when the optic portion is soft like the intraocular lens of thepresent invention, the above type having an angle of approximately 5 to10 degrees and the above wing type suffers the deformation of the opticportion and an increased displacement of the optic portion when thehaptic portion is compressed. Therefore, the haptic portion preferablyhas the form of a hopper for removing the deformation of the opticportion and the displacement of the optic portion when the hapticportion is compressed. The above form of the hopper will be specificallyexplained with reference to drawings later.

The process for the production of the above one-piece intraocular lensis not specially limited so long as there can be obtained a one-pieceintraocular lens having a structure in which the optic portion and thehaptic portion are formed of the above-explained materials andintegrated. However, when the following process of the present inventionis employed, there can be highly efficiently produced intraocular lensesof which the haptic portion is not easily removable and which are freeof a variability in product quality.

In the process of the present invention, (1) the optic-portion-formingmonomer mixture is polymerized with keeping the monomer mixture incontact with a haptic-portion-forming material containing PMMA, tointegrate the optic-portion-forming material and thehaptic-portion-forming material, and then, the integrated product is cutand polished to obtain an intended one-piece intraocular lens, or (2) ahaptic-portion-forming monomer containing methyl methacrylate ispolymerized with keeping the haptic-portion-forming monomer in contactwith an optic-portion-forming material formed of a copolymer obtained bypolymerization of the above monomer mixture, to integrate theoptic-portion-forming material and the haptic-portion-forming material,and then, the integrated product is cut and polished to obtain anintended one-piece intraocular lens.

According to the above process, an interpenetrating network (IPN)structure is formed in the junction of the optic-portion-formingmaterial and the haptic-portion-forming material, and as a result, inthe one-piece intraocular lens obtained as an end product, the hapticportion does not at all easily break away from the optic portion.

Since the optic-portion-forming material is soft, the cutting andpolishing are preferably carried out with cooling. That is, it ispreferred to carry out the cutting and polishing at a low-temperatureatmosphere of approximately −10 to 0° C.

In the above processes (1) and (2), the process (1) is particularlypreferred. For the process (1), for example, there is preferablyemployed a method in which a disc which is formed of PMMA and has acylindrical concave portion having predetermined dimensions is provided,the above optic-portion-forming monomer mixture is charged into theconcave portion, polymerized and then cut and polished with cooling, toproduce an intended one-piece intraocular lens.

The process for the production of the one-piece intraocular lens will bespecifically explained with reference to drawings hereinafter.

FIG. 1(a) is a perspective view of one example of a disc which is formedof PMMA and has a cylindrical concave portion, and FIG. 1(b) is a sideview of the same. FIG. 2(a) is a perspective view showing a state wherethe monomer mixture for forming the optic portion is charged in theconcave portion of the disc shown in FIG. 1, and FIG. 2(b) is a sideview showing the same. FIG. 3 is a perspective view for explaining thecutting of a material with a milling machine for a one-piece typeintraocular lens. FIG. 4(a) is a front view of one example of theintraocular lens (intraocular lens 1) of the present invention, and FIG.4(b) is a side view of the same.

First, a disc 1 which has a cylindrical concave portion 2 having adiameter of 6.2 mm, has a diameter of 16 mm and a thickness ofapproximately 5 mm as shown in FIG. 1 and is formed of PMMA is prepared.In FIG. 1, the cylindrical concave portion 2 has a diameter of 6.2 mm,while the form, diameter, etc., of the concave portion can be properlyselected depending upon the form of the optic portion of an intendedone-piece intraocular lens.

Further, the method of forming the above concave portion is notspecially limited, and the concave portion can be formed by means of amilling machine. However, it is advantageous to employ a method in whicha tool having a shape to be formed is prepared and the concave portionis formed in a disc by means of a press machine, since a complicatedform can be easily produced. Further, the disc material is also pressed(stretched), so that the tensile strength, etc., are improved. As aresult, the haptic portion can be improved in strength.

Then, as shown in FIG. 2, the above optic-portion-forming monomermixture 3 is charged into the cylindrical concave portion of the disc 1formed of PMMA, and the monomer mixture is polymerized by heating itapproximately from 40° C. to 120° C. After the polymerization iscompleted, a disc having a thickness of 3 mm was taken by cutting, andwith cooling, a base surface is cut. Then, with cooling, a material 5for a lens having the optic portion and the haptic portion integrated istaken by cutting with a milling machine as shown in FIG. 3. Then, withcooling a surface opposite to the base-cut surface, the front surface iscut, and further, the lens is barrel-polished at a low temperature,whereby there can be obtained the one-piece intraocular lens of thepresent invention in which the optic portion 6 and the hopper-shapedhaptic portion 7,7′ are integrated as shown in FIG. 4.

The soft intraocular lens (intraocular lens 2) of the present inventionwill be explained hereinafter.

The soft intraocular lens (intraocular lens 2) of the present inventionhas an optic portion which is formed of a deformable soft material andfunctions as a substitute lens for a crystalline lens and a hapticportion which is formed of arm-like members extending outwardly fromcircumferential portions of the optic portion and is for fixing andholding the optic portion in a predetermined position in an eye. And,the haptic portion has a bendable portion which, when a compressiveforce is externally exerted on the haptic portion so as to move at leastany site of the haptic portion toward the optic portion, can absorb atleast part of the external compressive force by deformation anddecreases the force to be transmitted to the optic portion.

The above bendable portion particularly preferably absorbs, bydeformation, at least part of a force which is exerted on the hapticportion so as to move the optic portion in a direction in parallel withthe optical axis of the optic portion.

Further, the soft intraocular lens preferably has a structure in whichthe above haptic portion is formed so as to form a first angle with aplane at right angles with the optical axis of the above optic portionas the haptic portion extends outwardly from its start portion in thevicinity of the above optic portion, and the above bendable portion hasa first bendable portion which is bent so as to form a second angle, anangle opposite to the above first angle, with a plane at right angleswith the optical axis of the optic portion in a position located outsidethe above start portion of the haptic portion and a second bendableportion which is bent so as to form a third angle, an angle opposite tothe above second angle, with a plane at right angles with the opticalaxis of the above optic portion in a position located outside the firstbendable portion.

In the soft intraocular lens (intraocular lens 2) having the abovestructure, the first angle is preferably 12 degrees or less, and thedistance from the start portion of the haptic portion to the firstbendable portion is preferably 3 mm or less.

The soft intraocular lens (intraocular lens 2) of the present inventionis particularly preferably a one-piece intraocular lens of which theoptic portion and the haptic portion are integrally formed. Further, thesoft intraocular lens preferably has the haptic portion formed of amaterial having a higher hardness than the hardness of a soft materialforming the optic portion.

FIGS. 5(a) and 5(b) show an example of configuration of the softintraocular lens (intraocular lens 2) of the present invention. FIG.5(a) is a plan view of the same, FIG. 5(b) is a side view of the same,and FIG. 6 is an enlarged view of part shown in FIG. 5(b).

In FIGS. 5(a) and 5(b), the soft intraocular lens is a one-piece softintraocular lens 8 having an optic portion 6 and an arm-like hapticportion 7,7′ extending outwardly from circumferential portions of theoptic portion 6, the optic and haptic portions being integrally formed.

The optic portion 6 is a circular convex lens formed of a soft opticportion material to be described later and has an outer diameter ofapproximately 5.0 to 6.5 mm.

The haptic portion 7,7′ is formed of PMMA and formed of two arm-likemembers extending from two sites which are on circumferential portionsof the optic portion 6 and have a central point symmetrical relationshipwith regard to the center O of the optic portion 6. As shown in FIG.5(a), the haptic portion 7,7′ when viewed as a plan view has a curvedform which extends outwardly from a start portion 71,71′ located in aboundary formed with the optic portion 6 while decreasing the ratio ofclearance from the optic portion and which therefore nearly forms aconcentric circle with the optic portion in the vicinity of its endportion.

In the form of the haptic portion 7,7′ when viewed as a side view, asshown in FIG. 5(b) and FIG. 6, the haptic portion 7,7′ extends outwardlyfrom a base of the start portion 71,71′ and forms an angle α₁ with aplane at right angles with the optical axis of the optic portion 6, afirst bendable portion 72,72′ is formed at a distance “a” from the base,and a second bendable portion 73,73′ is formed at a distance “b” from atangent line on a site which is near the top portion thereof and has anearly concentric circle relationship with the optic portion 6. Thatportion of the haptic portion 7,7′ which is positioned outside thesecond bendable portion 73,73′ is formed so as to be nearly in parallelwith a plane at right angles with the optical axis.

The above distance “a” preferably set at 3 mm or less. The above angleα₁ is preferably set at 12 degrees or less. The distance “b” isgenerally set at several millimeters. Further, the bending angle of thefirst bendable portion 72,72′ is set such that the portion locatedbetween the first bendable portion 72,72′ and the second bendableportion 73,73′ forms an angle of α₂ with a plane in perpendicular withthe above optical axis. The bending angle of the second bendable portionis set at such an angle that the portion located outside the secondbendable portion 73,73′ is nearly in parallel with a plane at rightangles with the optical axis. When a straight line formed by connectingthe top end of the haptic portion 7,7′ and a circumferential end portionof the optic portion forms an angle β with a plane at right angles withthe above optical axis, the above α₂ is preferably set such that theabove β is approximately 5 degrees.

The above-structured one-piece soft intraocular lens can be produced inthe same manner as in the production of the one-piece intraocular lens(intraocular lens 1) of the present invention.

The present invention will be explained in detail with reference toExamples, while the present invention shall not be limited by theseExamples.

EXAMPLE 1

A monomer mixture for forming an optic portion was prepared by mixing

2-phenylethyl methacrylate (PEMA)  56 parts by weight n-butyl acrylate(BA)  35 parts by weight 2-[2-(perfluorooctyl)ethoxy-1-   9 parts byweight methylethyl methacrylate (BRM) ethylene glycol dimethacrylate(EDMA)   3 parts by weight and azobisisobutyronitrile (AIBN) 0.3 part byweight.

There was provided a disc which had a cylindrical concave portion havinga diameter of 6.2 mm and had a diameter of 16 mm and a thickness ofapproximately 5 mm as shown in FIG. 1 and which was formed of PMMA. Theabove monomer mixture was charged in the concave portion of the abovedisc and polymerized under pressure at a nitrogen pressure of 2.0 kg/cm²at a temperature of 60° C. for 2 hours, and then, the polymerizedproduct was maintained at 80° C. for 2 hours and then at 100° C. for 2hours to complete the polymerization.

Then, a 3 mm thick disc was taken by cutting, and an optical surface wascut with blowing cold air of −5° C. to the disc. With blowing cold airagain, the disc was cut with a milling machine as shown in FIG. 3, andwhile cold air was blown to the surface opposite to the surface cut withthe milling machine, the optical surface was cut. In this case, ahopper-shaped haptic portion was formed.

The so-obtained lens was barrel-polished in a constant-temperaturechamber at −5° C. for 3 days, to give a one-piece intraocular lens shownin FIG. 4.

Table 1 shows the appearance, the self-adhesion, the formrestoration-capability and the refractive index of the above one-pieceintraocular lens.

EXAMPLES 2-8

One-piece intraocular lenses were prepared in the same manner as inExample 1 except that the monomer mixture for forming an optic portionwas changed as shown in FIGS. 1 or 2.

Tables 1 and 2 show the appearance, the self-adhesion, the formrestoration capability and the refractive index of the above one-pieceintraocular lenses.

TABLE 1 Example 1 2 3 4 Composition of monomer mixture (wt %) BRM 1) 9 78 8 PEMA2) 56 50 62 46 BA 3) 35 43 30 46 ERA 4) — — — — CHMP5) — 0.5 0.50.5 EDMA6) 3 3 3 3 AIBN 7) 0.3 0.3 0.3 0.3 Appearance Trans- Trans-Trans- Trans- parent parent parent parent Self-adhesion 8) Nil Nil NilNil Form restoration 45 28 52 25 capability 9) (second) Refractive index10) 1.512 1.506 1.520 1.504

TABLE 2 Example 5 6 7 8 Composition of monomer mixture (wt %) BRM 1) 1010 8 15 PEMA 2) 49 50 55 47 BA 3) 41 — — — ERA 4) — 40 37 38 CHMP 5) 0.50.5 0.5 0.5 EDMA 6) 3 3 3 3 AIBN 7) 0.3 0.3 0.3 0.3 Appearance Trans-Trans- Trans- Trans- parent parent parent parent Self-adhesion 8) NilNil Nil Nil Form restoration 33 35 48 37 capability 9) (second)Refractive index 10) 1.502 1.504 1.510 1.497 Notes to Tables 1 and 2: 1)BRM: 2-[2-(perfluorooctyl)ethoxy]-1-methylethyl methacrylate 2) PEMA:2-phenylethyl methacrylate 3) BA: n-butyl acrylate 4) EHA: 2-ethylhexylacrylate 5) CHMP:5-chloro-2-[2-hydroxy-5-(β-methacryloyl-oxyethylcarbamoyloxyethyl)]phenyl-2H-benzotriazole6) EDMA: ethylene glycol dimethacrylate 7) AIBN: azobisisobutyronitrile8) Self-adhesion: The optic portion of an intraocular lens was bent withan intraocular lens bending nipper, and the optic portion did not showself-adhesion when released was taken as no-adhesion. 9) Formrestoration capability: The optic portion of an intraocular lens wasbent with an intraocular lens bending nipper, and a time taken until theoptic portion restored its original diameter was used. 10) Refractiveindex: An intraocular lens was measured for a refractive index withe-ray (546.1 nm) at 36° C. with a refractometer supplied by Atago Co.

EXAMPLE 9

A monomer mixture for forming an optic portion was prepared by mixing

n-butyl acrylate  42 parts by weight phenyl ethyl methacrylate  49 partsby weight perfluorooctylethyloxypropylene methacrylate   9 parts byweight ethylene glycol dimethacrylate   3 parts by weight andazobisisobytyronitrile 0.3 part by weight.

There was provided a disc which had a cylindrical concave portion havinga diameter of 6.5 mm and had a diameter of 16.5 mm and a thickness ofapproximately 5 mm as shown in FIG. 1 and which was formed of PMMA. Theabove monomer mixture was charged in the concave portion of the abovedisc and polymerized under pressure at a nitrogen pressure of 2.0 kg/cm²at a temperature of 60° C. for 2 hours, and then, the polymerizedproduct was maintained at 80° C. for 2 hours and then at 100° C. for 2hours to complete the polymerization.

Then, a 3 mm thick disc was taken by cutting, and an optical surface wascut with blowing cold air of −10° C. to the disc. With blowing cold airagain, the disc was cut in the form of one piece with a milling machineas shown in FIG. 3, whereby a lens having a predetermined optic portionform and a predetermined haptic portion form were obtained.

The so-obtained lens was barrel-polished for 5 days, to give a one-pieceintraocular lens shown in FIGS. 5 and 6.

The distance “a” was 1 mm, the angle α₁ was approximately 5 degrees, thedistance “b” was 1.5 mm, and the angle α₂ was approximately 17 degrees.

EXAMPLE 10

A one-piece soft intraocular lens was obtained in the same manner as inExample 9 except that the angle α₁ was changed to approximately 10degrees and that the angle α₂ was changed to approximately 29 degrees.

COMPARATIVE EXAMPLE 1

A one-piece soft intraocular lens was obtained in the same manner as inExample 9 except that the form of a haptic portion was changed to aconventional type as shown in FIG. 8 and that α was set at 5 degrees.

COMPARATIVE EXAMPLE 2

A one-piece soft intraocular lens was obtained in the same manner as inExample 9 except that the form of a haptic portion was changed to aconventional wing type as shown in FIG. 9 and that a was set at 10degrees.

COMPARATIVE EXAMPLE 3

A one-piece intraocular lens having an optic portion and a hapticportion which were integrally formed of PMMA and whose haptic portionhad a conventional form (α=5 degrees) as shown in FIG. 8 was used asComparative Example 3.

COMPARATIVE EXAMPLE 4

A one-piece intraocular lens having an optic portion and a hapticportion which were integrally formed of PMMA and whose haptic portionhad a conventional wing type form (α=10 degrees) as shown in FIG. 9 wasused as

COMPARATIVE EXAMPLE 4.

The intraocular lenses in Examples 9 and 10 and Comparative Examples 1to 4 were tested as follows.

(1) Resolution/Power Test

A lens was fixed in a ring having a diameter of 10 mm and measured for aresolution and a power (lens strength).

The results of the above measurement were as follows. Each of theintraocular lenses in Examples 9 and 10 and Comparative Examples 3 and 4was fit in the ring having a diameter of 10 mm, and it was found thatthese lenses had a resolution and a power as designed. In theintraocular lenses obtained in Comparative Examples 1 and 2, however,the optic portion was deformed since the optic portion gradually floatedafter the lens was fixed in the ring having a diameter of 10 mm.Therefore, the lenses in Comparative Examples 1 and 2 were notmeasurable for a resolution and a power in the ring having a diameter of10 mm.

(2) Holding Test Under Compression

As shown in FIG. 10, a lens 8 was set in a tool 9 whose holding diameterwas variable, and the lens was compressed by decreasing the holdingdiameter of the tool 9 to 11 mm and to 10 mm. In this case, the opticportion was measured for a distance of movement of the center of theoptic portion in the optical axis direction with a digital measuringmicroscope (STM 5-322, supplied by Olympus Optical Co., Ltd.).

The results of the above holding test under compression were as shown inFIG. 11. As shown in FIG. 11, the intraocular lenses in Examples 9 and10 showed almost no difference at any time of the compression to adiameter of 11 mm and the compression to a diameter of 10 mm and wereremarkably excellent when compared with the conventional one-piece typelens (α=5 degrees) formed of PMMA (optic portion was also formed ofPMMA—hard material) shown in FIG. 8 and the wing type lens (α=10degrees) shown in FIG. 9 (Comparative Examples 3 and 4).

However, the lens having an optic portion formed of the soft materialand a haptic portion shown in FIG. 8 (α=5 degrees) and the lens havingan optic portion formed of the soft material and a wing type hapticportion shown in FIG. 9 (α=10 degrees), i.e., the lenses in ComparativeExamples 1 and 2, showed a large movement of their optic portions in theoptical axis direction and suffered deformation when compressed to adiameter of 10 mm.

The above results are obtained presumably due to the following function.That is, in the conventional type lens shown in FIG. 8, whose opticportion is formed of a soft material, as shown in FIG. 12(a), thecompressive force exerted on the haptic portion is directly transmittedin the longitudinal direction of the haptic portion to reach the opticportion and causes the optic portion to rise in the optical axisdirection or deforms the optic portion.

In the conventional wing type lens shown in FIG. 9, whose optic portionis formed of a soft material, as shown in FIG. 12(b), the compressiveforce exerted on the haptic portion is once dispersed, but a major partof the compressive force is transmitted to the optic portion since thedispersion is insufficient, and it causes the optic portion to rise inthe optical axis direction or deforms the optic portion.

In contrast, in the lenses obtained in Examples of the presentinvention, as shown in FIG. 12(c), the compressive force is dispersedtwice before it reaches the optic portion and the force to be exerted onthe optic portion is moderated.

Industrial Utility

In the intraocular lens (intraocular lens 1) of the present invention,the optic portion is soft, and when it is bent and then released, theoptic portion does not undergo self adhesion and restores its originalshape in 20 to 60 seconds. Therefore, there is produced an effect thatthe intraocular lens of the present invention is free from damaging acapsule after inserted in an eye.

According to the process of the present invention, further, it is notrequired to provide the step of hydrating the optic portion, nor is itrequired to provide the step of esterification, after a one-pieceintraocular lens is produced. The angle of the haptic portion can betherefore maintained, and one-piece intraocular lenses having hard andstrong haptic portions can be highly efficiently produced without avariability in product quality in simple steps.

According to the process of the present invention, further, theone-piece intraocular lens can be produced in the same method as thatemployed in the production of conventional one-piece types by onlycooling in cutting and polishing steps.

Further, the soft intraocular lens (intraocular lens 2) of the presentinvention has a characteristic feature in that the intraocular lens hasa haptic portion provided with a bendable portion which, when acompressive force is externally exerted on the haptic portion so as tomove at least any site of the haptic portion toward the optic portion,can absorb at least part of the external compressive force bydeformation and decreases the force to be transmitted to the opticportion. As a result, when a capsule shrinks after the above softintraocular lens is inserted in the capsule, the optic portion undergoesneither deformation nor distortion.

What is claimed is:
 1. A one piece intraocular lens having an opticportion which functions as a substitute lens for a crystalline lens anda haptic portion for fixing and holding the optic portion in apredetermined position in an eye, the optic portion having an opticalaxis and being formed of a copolymer obtained by polymerization of amonomer mixture containing (a) 5 to 20% by weight of2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of the formula(I),

wherein R¹ is hydrogen or methyl, (b) 40 to 70% by weight of2-phenylethyl (meth)acrylate of the formula (II),

wherein R² is hydrogen or methyl, (c) 25 to 50% by weight of alkyl(meth)acrylate of the formula (III)

wherein R³ is hydrogen or methyl and R⁴ is a C₄-C₁₂ linear, branched orcyclic alkyl group, and (d) 0.5 to 5% by weight, based on the totalamount of the components (a) to (c), of a crosslinking monomer, thehaptic portion is formed of polymethyl methacrylate and has a firstangle with a plane at right angles with the optical axis of the opticportion and through an optical center of the lens as the haptic portionextends outwardly from its start portion in the vicinity of the opticportion, and the haptic portion has a first bendable portion which isbent so as to form a second angle, an angle opposite to the first angle,with said plane in a position located outside the start portion of thehaptic portion and a second bendable portion which is bent so as to forma third angle, an angle opposite to the second angle, with said plane ina position located outside the first bendable portion, wherein at leastthe first and second bendable portions of the haptic portion from aproximal end to a distal end extend radially farther away from theoptical center of the lens.
 2. The one-piece intraocular lens of claim1, wherein the optic portion has deformable softness.
 3. The one-pieceintraocular lens of claim 1, wherein the optic portion and the hapticportion have a junction portion formed of an interpenetrating networkstructure.
 4. A process for the production of a one-piece intraocularlens having an optic portion which functions as a substitute lens for acrystalline lens and a haptic portion for fixing and holding the opticportion in a predetermined position in an eye, the optic portion havingan optical axis, wherein the haptic portion has a first angle with aplane at right angles with the optical axis of the optic portion andthrough an optical center of the lens as the haptic portion extendsoutwardly from its start portion in the vicinity of the optic portion,and the haptic portion has a first bendable portion which is bent so asto form a second angle, an angle opposite to the first angle, with saidplane in a position located outside the start portion of the hapticportion and a second bendable portion which is bent so as to form athird angle, an angle opposite to the second angle, with said plane in aposition located outside the first bendable portion, wherein at leastthe first and second bendable portions of the haptic portion from aproximal end to a distal end extend radially farther away from theoptical center of the lens, the process comprising polymerizing anoptic-portion-forming monomer mixture containing: (a) 5 to 20% by weightof 2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of theformula (I),

wherein R¹ hydrogen or methyl, (b) 40 to 70% by weight of 2-phenylethyl(meth)acrylate of the formula (II),

wherein R² is hydrogen or methyl, (c) 25 to 50% by weight of alkyl(meth)acrylate of the formula (III)

wherein R³ is hydrogen or methyl and R⁴ is a C₄-C₁₂ linear, branched orcyclic alkyl group, and (d) 0.5 to 5% by weight, based on the totalamount of the components (a) to (c), of a crosslinking monomer, whilekeeping the monomer mixture in contact with a haptic-portion-formingmaterial containing polymethyl methacrylate, or polymerizing ahaptic-portion-forming monomer containing methyl methacrylate whilekeeping the haptic-portion-forming monomer in contact with anoptic-portion-forming material formed of a copolymer obtained bypolymerization of the above monomer mixture, to integrate theoptic-portion-forming material and the haptic-portion-forming material,and thereafter cutting and polishing the integrated product.
 5. Theprocess of claim 4, wherein a disc which is formed of polymethylmethacrylate and has a cylindrical concave portion having predetermineddimensions is provided and the monomer mixture is charged in thecylindrical concave portion and polymerized.
 6. The process of claim 4,wherein the cutting and polishing are carried out with cooling.
 7. Asoft intraocular lens having an optic portion formed of a deformablesoft material which functions as a substitute lens for a crystallinelens and a haptic portion which is formed of arm members extendingoutwardly from circumferential portions of the optic portion and is forfixing and holding the optic portion in a predetermined position in aneye, the optic portion having an optical axis, wherein the hapticportion has a first angle with a plane at right angles with the opticalaxis of the optic portion and through an optical center of the lens asthe haptic portion extends outwardly from its start portion in thevicinity of the optic portion, and the haptic portion has a firstbendable portion which is bent so as to form a second angle, an angleopposite to the first angle, with said plane in a position locatedoutside the start portion of the haptic portion and a second bendableportion which is bent so as to form a third angle, an angle opposite tothe second angle, with said plane in a position located outside thefirst bendable portion, wherein at least the first and the secondbendable portions of the haptic portion from a proximal end to a distalend extend radially farther away from the optical center of the lens,and when a compressive force is externally exerted on the haptic portionso as to move at least any site of the haptic portion toward the opticportion, the haptic portion can absorb at least part of the externalcompressive force by deformation which decreases the force to betransmitted to the optic portion.
 8. The soft intraocular lens of claim7, wherein when force is applied to the lens and transmitted to theoptic portion to move the optic portion in a direction in parallel withan optical axis of the optic portion, the bendable portion deforms andabsorbs at least part of the applied force.
 9. The soft intraocular lensof claim 7, wherein the first angle is 12 degrees or less.
 10. The softintraocular lens of claim 7, wherein the distance from the start portionof the haptic portion to the first bendable portion is 3 mm or less. 11.The soft intraocular lens of claim 7, wherein the optic portion and thehaptic portion are integrally formed.
 12. The soft intraocular lens ofclaim 7, wherein the haptic portion is formed of a hard material havinga higher hardness than a soft material forming the optic portion.
 13. Asoft intraocular lens having an optic portion formed of a deformablesoft material which functions as a substitute lens for a crystallinelens and a haptic portion which is formed of arm members extendingoutwardly from circumferential portions of the optic portion and is forfixing and holding the optic portion in a predetermined position in aneye, the optic portion having an optical axis, wherein the hapticportion has a first angle with a plane which passes a start portion ofthe haptic portion and which is in the direction at right angles withthe optical axis of the optic portion, the haptic portion extendingoutwardly from the start portion in the vicinity of the optic portion,and the haptic portion has a first bendable portion which is bent so asto form a second angle, an angle opposite to the first angle, with saidplane in a position located outside the start portion of the hapticportion and a second bendable portion which is bent so as to form athird angle, an angle opposite to the second angle, with said plane in aposition located outside the first bendable portion, the haptic portionthus crossing an imaginary line parallel to said plane and extendingthrough an optical center of the lens, wherein each bendable portion ofthe haptic portion extends away from the optical center of the lens, andwhen a compressive force is externally exerted on the haptic portion soas to move at least any site of the haptic portion toward the opticportion, the haptic portion can absorb at least part of the externalcompressive force by deformation which decreases the force to betransmitted to the optic portion.
 14. The soft intraocular lens of claim13, wherein the optic portion is formed of a copolymer obtained bypolymerization of a monomer mixture containing (a) 5 to 20% by weight of2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of the formula(I),

wherein R¹ is hydrogen or methyl, (b) 40 to 70% by weight of2-phenylethyl (meth)acrylate of the formula (II),

wherein R² is hydrogen or methyl, (c) 25 to 50% by weight of alkyl(meth)acrylate of the formula (III)

wherein R³ is hydrogen or methyl and R⁴ is a C₄-C₁₂ linear, branched orcyclic alkyl group, and (d) 0.5 to 5% by weight, based on the totalamount of the components (a) to (c), of a crosslinking monomer.
 15. Thesoft intraocular lens of claim 13 wherein the first angle is 12 degreesor less.
 16. The soft intraocular lens of claim 13, wherein the distancefrom the start portion of the haptic portion to the first bendableportion is 3 mm or less.
 17. The soft intraocular lens of claim 13,wherein the optic portion and the haptic portion are integrally formed.18. The soft intraocular lens of claim 13, wherein the haptic portion isformed of a hard material having a higher hardness than a soft materialforming the optic portion.
 19. The process of claim 4, wherein thehaptic-portion-forming material is pressed before the monomer mixture isbrought into contact with the haptic-portion-forming material.
 20. Aprocess for the production of a one-piece intraocular lens having anoptic portion which functions as a substitute lens for a crystallinelens and a haptic portion for fixing and holding the optic portion in apredetermined position in an eye, the optic portion having an opticalaxis, the process comprising polymerizing an optic-portion-formingmonomer mixture containing: (a) 5 to 20% by weight of2-[2-(perfluorooctyl)ethoxy]-1-methylethyl (meth)acrylate of the formula(I),

wherein R¹ hydrogen or methyl, (b) 40 to 70% by weight of 2-phenylethyl(meth)acrylate of the formula (II),

wherein R² is hydrogen or methyl, (c) 25 to 50% by weight of alkyl(meth)acrylate of the formula (III)

wherein R³ is hydrogen or methyl and R⁴ is a C₄-C₁₂ linear, branched orcyclic alkyl group, and (d) 0.5 to 5% by weight, based on the totalamount of the components (a) to (c), of a crosslinking monomer, whilekeeping the monomer mixture in contact with a haptic-portion-formingmaterial containing polymethyl methacrylate, or polymerizing ahaptic-portion-forming monomer containing methyl methacrylate whilekeeping the haptic-portion-forming monomer in contact with anoptic-portion-forming material formed of a copolymer obtained bypolymerization of the above monomer mixture, to integrate theoptic-portion-forming material and the haptic-portion-forming material,and thereafter cutting and polishing the integrated product wherein thehaptic portion has a first angle with a plane which passes a startportion of the haptic portion and which is in the direction at rightangles with the optical axis of the optic portion, the haptic portionextending outwardly from the start portion in the vicinity of the opticportion, and the haptic portion has a first bendable portion which isbent so as to form a second angle, an angle opposite to the first angle,with said plane in a position located outside the start portion of thehaptic portion and a second bendable portion which is bent so as to forma third angle, an angle opposite to the second angle, with said plane ina position located outside the first bendable portion, the hapticportion thus crossing an imaginary line parallel to said plane andextending through an optical center of the lens, wherein each bendableportion of the haptic portion extends away from the optical center ofthe lens, and when a compressive force is externally exerted on thehaptic portion so as to move at least any site of the haptic portiontoward the optic portion, the haptic portion can absorb at least part ofthe external compressive force by deformation which decreases the forceto be transmitted to the optic portion.
 21. A soft intraocular lenshaving an optic portion formed of a deformable soft material whichfunctions as a substitute lens for a crystalline lens and a hapticportion which is formed of arm members extending outwardly fromcircumferential portions of the optic portion and is for fixing andholding the optic portion in a predetermined position in an eye, theoptic portion having an optical axis, wherein the haptic portion has afirst angle with a plane which passes a start portion of the hapticportion and which is in the direction at right angles with the opticalaxis of the optic portion, the haptic portion extending outwardly fromthe start portion in the vicinity of the optic portion, and the hapticportion has a first bendable portion which is bent so as to form asecond angle, an angle opposite to the first angle, with said plane in aposition located outside the start portion of the haptic portion and asecond bendable portion which is bent so as to form a third angle, anangle opposite to the second angle, with said plane in a positionlocated outside the first bendable portion, the haptic portion thuscrossing an imaginary line parallel to said plane and extending throughan optical center of the lens, wherein each bendable portion of thehaptic portion extends away from the optical center of the lens, andwherein that portion of each haptic portion which is positioned outsidethe second bendable portion is formed so as to be nearly in parallelwith a plane at right angles with the optical axis, and when acompressive force is externally exerted on the haptic portion so as tomove at least any site of the haptic portion toward the optic portion,the haptic portion can absorb at least part of the external compressiveforce by deformation which decreases the force to be transmitted to theoptic portion.
 22. A The soft intraocular lens of claim 21, wherein theoptic portion has deformable hardness.
 23. The soft intraocular lens ofclaim 21, wherein the first angle is 12 degrees or less.
 24. The softintraocular lens of claim 21, wherein the distance from the startportion of the haptic portion to the first bendable portion is 3 mm orless.
 25. The soft intraocular lens of claim 21, wherein the opticportion and the haptic portion are integrally formed.
 26. The softintraocular lens of claim 21, wherein the haptic portion is formed of ahard material having a higher hardness than a soft material forming theoptic portion.